[Some mild spoilers for The Last Jedi, if that still matters right now.]
To be clear: I don't want him to have a redemption arc per se. I adore Hux for what he is and what he is happens to absolutely despicable. I love how awful he is and never more so than in that little moment when he finds Snoke dead and Ren unconscious and just casually reaches for his sidearm. Sadly for him, Ren wakes up and you can see the exasperation on Hux's face.
Hux hates everyone. He hates the Republic, he hates the Resistance and he absolutely despises Kylo Ren.
He obviously needs to betray Ren sometime in the future and the funniest version of this would be him defecting to the Resistance. Not because he has any sort of change of heart or positive character development. No! Out of spite. Pure, unadulterated spite because that's why Hux runs on. Well, spite and daddy issues.
No, seriously, just listen to how Domhnall Gleeson delivers the line about receiving his orders directly from Supreme Leader Snoke at the beginning of TLJ. Daddy issues, you don't even need to read any of the Eu stuff about his abusive father.
Now imagine him working with the Resistance. Imagine him standing at a holo-table with Finn, Rey and Poe as he describes how to take out the latest First Order superweapon. He starts off reasonable “As you can see the weak spot is here at the base of the power converter array,” but he can't quite keep old habits out, “and so if your MONGREL REBEL SCUM FIGHTER SQUADRONS focus fire on the...” and then he trails off as he sees the looks everyone is giving him. Then he delicately clears his throat and very, very quietly apologises.
And of course there'd have to be compulsory scene where he and Poe are trapped together in a ship arguing about an immediate life or death situation.
In desperation for that sense of power he misses so much he starts drilling the Millennium Falcon's porg population into an elite fighting force.